Cellulose mixed ester compositions containing higher fatty acid esters



Patented Feb. 15, 1938 mural)'s'rm'ias' PATENT OFFICE CONTAINING HIGHER FATTY ESTERS ACID Jersey No Drawing. Application May 16, 1934,

Serial No. 725,955,

7 Claims. o1. 106- 40 This invention relates to plasticizers for mixed organic esters of cellulose, such, for instance, as cellulose acetate-propionate, cellulose acetatebutyrate, cellulose acetate-stearate and the like.

5 One object of the invention is to provide cellulose mixed ester compositions from which flexible sheets and other useful plastic products may be made. Another object is to provide flexible sheets of cellulose mixed esters, such as are useful for l photographic film, wrapping sheets, etc. Other objects will hereinafter appear.

Cellulose acetate-propionate has become known only within the last few years, and the field of plasticizers for it and for other mixed l esters of cellulose is, as yet, not well explored, although certain plasticizers for these esters have recently been discovered, such, for instance, as

tri-o-diphenyl phosphate, diamyl hydroquinone,

mono-butyl glyceryl oleate, ethoxyethyl laurate, 20 diacetyl glyceryl stearate, ethoxyethyl stearate, ethylene glycol dilaurate and chlorinated paraffin oil.

Fully esterifled cellulose acetate-propionate, cellulose acetate-butyrate, etc., may be prepared as described in Clark & Malms U. S. Patent No. 1,800,860. The preparation of partially hydrolyzed cellulose acetate-propionate and other mixed esters, i. e., cellulose acetate-propionate, etc. from which a portion of the acyl groups has 30 been hydrolyzed off, is described in the co-pending application of Carl J. Malm and Charles E.

Fletcher, Serial No. 551,546, now Patent No.

. 2,026,583. Cellulose acetate-stearate may be prepared as described in the co-pending application 35 of Hans T. Clarke and Carl J. Malm, Serial No.

520,150, Patent No. 1,987,053.

Cellulose acetate-propionate, acetate-butyrate,

etc. have properties differing from those of cellulose acetate.. For instance, propylene chloride 40 and ethylene chloride, which alone are not solvents for cellulose acetate-either fully esterified or partially hydrolyzed-readily dissolve a majority of these cellulose esters, whether fully esterihad or partially hydrolyzed, and sheets coated' 45 from such solutions, even without a plasticizer,

show fair flexibility, as is disclosed in the copending application of Carl J. Malm, Serial No. 551,545, Patent No. 2,006,362. Furthermore, acetone is a solvent for unhydrolyzed or fully esteri- 50 fled cellulose acetate-propionate, although sheets coated from such solutions are brittle, whereas unhydrolyzed cellulose acetate is not soluble in acetone.

Consistently with the unexpected behavior of 55 the cellulose mixed esters, I have now found that lent plasticizers for cellulose acetate-propionate,

cellulose acetate-butyrate, etc. The methyl, ethyl, propyl and butyl esters of the saturated 5 fatty acids of from 12 to 18 carbon atoms, 1. e., of the fatty acids from lauric to stearic, inclusive, while some few of them may be compatible with cellulose nitrate, are incompatible with the only commercially-used form of cellulose acetate, namely, acetone-soluble cellulose acetate, and, consequently, nowhere in the art have they ever been suggested as components of cellulose acetate compositions. Fully esterified cellulose acetate, even when combined with plasticizers, is not commercially valuable. Contrary to expectation, I have discovered that these fatty acid alkyl esters are compatible with a certain range of acetonesoluble cellulose acetate-propionate, cellulose acetate-butyrate, cellulose. acetate-stearate, etc., 20 namely, the fully esterified cellulose mixed esters and those so slightly hydrolyzed-that they contain less than 1.5 esteriflable hydroxyl/groups per 24 carbon atoms of the cellulose radical. The upper limit of hydrolysis to which the cellulose 25 mixed esters may be subjected accordingto the. process of the above-mentioned Malm and Fletcher application No. 551,546 and still be compatible with my novel plasticizers, is approximately 50 hours hydrolysis.

The ratio of acetyl radical to higher fatty acid radical in the cellulose mixed ester may be varied within wide limits, the compatibility of my novel plasticizers being dependent on the complete or nearly complete esterification of the cellulose in the cellulose mixed ester rather than on any particular ratio of higher fatty acid radical to acetyl radical. For instance, I have found my novel plasticizers to be compatible with substantially fully esterified cellulose acetate-propionate whose 4v composition varies all the way from 39.4% acetyl group and 5.3% propionyl group to 14.3% acetyl group-and 35% propionyl group (based on the complete ester). However, when any of the mixed esters is hydrolyzed to such an extent asto contain as high as 1.5 esterifiable hydroxyl groups per 24 carbon atoms of the cellulose radical, incompatibility of the plasticizers results.

In order that those skilled in the art may better understand my invention I would state, by way 0 of illustration, that for the manufacture of photographic film base or other sheets my new compositions of matter may be compounded as follows: 100 parts by weight of substantially fully esterified cellulose acetate-propionate is dissolved with stirring infrom 500 to 600 parts by weight of ethylene chloride or of a mixture of ethylene chloride and'10% methanol. To this solution may be added from 5 to 25 parts by weight of the methyl, ethyl, propyl or butyl ester of a saturated fatty acid having from 12 to 18 carbon atoms, such for instance as a laurate, palmitate or stearate. Within the limits -stated, the amount of plasticizer may be decreased or increased, depending upon whether it is desired to decrease or increase, respectively, the properties which these plasticizers contribute to the finished product. The amount of solvent employed may also be increased or decreased, depending upon whether it is desired to have a more or less freely flowing composition, respectively.

A composition of matter prepared as above described may be deposited upon any suitable filmforming surface to form a film or sheet, in a manner well known to those skilled in the art. A film so produced has permanently brilliant transparency and low inflammability, burning no more readily than ordinary newsprint. Films or sheets produced in accordance with my invention are tough and extremely flexible. For instance,

films of cellulose acetate-propionate which have been hydrolyzed in accordance with the disclosure of the above-named Malm and Fletcher application for 50 hours, plasticized with from 5% to 25% of methyl laurate (parts by weight based on the weight of the cellulose ester), had an initial flexibility of from 350% to 700% of that of a film oi the same cellulose ester with no plasticizer, and a film containing 5% of methyl 'stearate had an initial flexibility of 375% of that of the unplasticized film. Films of fully esterlfled cellulose acetate-propionate containing from 10% to 20% of plasticizer showed the following flexibilities, compared with that of an unplasticized film of the same cellulose ester: butyl stearate, 250-575%; ethyl stearate, 375-575%; methyl stearate,'450-575%; ethyl laurate, 300- 575%; methyl laurate, 425-600%; ethyl palmitate, 575-750%; methyl palmitate, SOD-575%. Films of fully esterifled cellulose acetate-butyrate containing 25% of methyl stearate or methyl palmitate had a flexibility of 600%, a film containing 25% of ethyl laurate had a flexibility of 300%, and a fllm containing 25% oi methyl laurate had a flexibility of 350% of the flexibility of an unplasticized film of the same cellulose ester. In preparing these films, unplasticiz'ed as well as plasticized, ethylene chloride was used as the solvent for the fully esterified cellulose esters, and a 90:10 mixture of ethylene chloride and methanol for the slightly hydrolyzed cellulose acetate-propionate.

Furthermore, films plasticized with my novel plasticizers maintain flexibility in a superior fashion. For instance, all of the fully esterified cellulose acetate-propionate films described above still showed satisfactory flexibility after being kept at 65 C. for 170 days, whereas an unplasticized film of the same cellulose ester had become brittle at the end of 30 days. This indicates that films so plasticized will withstand ordinary usage satisfactorily for many years.

amass:

other solvents which are compatible with the cellulose ester being used, and with the piasticizer, may be employed instead of those'mentioned above. Other mixed esters of cellulose. such, for instance, as cellulose acetate-stearate, showed similar results.

While I have described themanufacture of films and sheets from my new compositions, it will be apparent that they may be employed with advantage in the other branches of the plastic art, such, for instance, as in the manufacture of lacquers What I claim as my invention and desire to be secured by Letters Patent of the United States is: e

l. A transparent, flexible sheet comprising parts by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esteriflable hydroxyl groups per 24 carbon atoms of the cellulose radical, and, as a plasticizer therefor, from 5 to 25 parts by weight of an ester of a fatty acid of from 12 to 18 carbon atoms with a monohydric alcohol of from one to four carbon atoms.

2. A transparent, flexible sheet comprising 100 parts by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esteriflable hydroxyl groups per 24 carbon atoms of the cellulose radical, and, as a. plasticizer therefor, from 5 to 25 parts by weight of a stearic acid ester of a monohydric alcohol of from one to four carbon atoms.

3. A transparent, flexible sheet comprising 100 parts by weight of a cellulose mixedester of fatty acids containing less than 1.5 esteriflable hydroxyl groups per 24 carbon atoms of the cellulose radical, and, as a plasticizer therefor, from 5 to 25 parts by weight of a palmitic acid ester of a monohydric alcohol of from one to four carbon atoms.

4. A transparent, flexible sheet comprisinglOO parts'by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esteriflable hydroxyl groups per 24 carbon atoms of the cellulose radical, and, as a plasticizer therefor, from 5 to 25 parts by weight of a lauric acid ester of a monohydric alcohol of from one to four carbon atoms.

5. A transparent, flexible sheet comprising 100 parts by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esteriflable hydroxyl groups per 24 carbon atoms of the cellulose radical, and, as a plasticizer therefor, from 5 to.25 parts by weight of methyl stearate.

6. A transparent, flexible sheet comprising 100 parts by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esteriflable hydroxylgroups per 24 carbon atoms of the cellulose radical, and, as a plasticizer therefor, from 5 to'25 parts by weight of methyl pallnitate.

7. A transparent, flexible sheet comprising 100 parts by weight of a cellulose mixed ester of fatty acids containing less than 1.5 esterifiable' hydroxyl groups per 24 carbon atoms of the cellulose radical, ancl, as a. plasticizer therefor, from 5 to 25 parts by weight of methyl laurate.

EGENRY B. SMITH. 

